Gibberellin Structure-Dependent Interaction between Gibberellins and Deoxygibberellin C in the Growth of Dwarf Maize Seedlings

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RESUMO

The effects of 3-deoxygibberellin C (DGC) on the growth-promoting actions of gibberellins A1, A2, A3, A4, A5, A7, A8, A9, A13, A18, A19, A20, and A23 (GAn) as well as 13-deoxygibberellin A5 (deoxy-GA5) were tested with seedlings of gibberellin-deficient dwarf mutants (d2 and d5) of maize (Zea mays L.). It was found that DGC promoted the actions of gibberellins having both C-1 double bond and C-3 axial hydroxyl group, and it inhibited the action of gibberellins having the saturated ring A and lacking the C-3 axial hydroxyl group, whereas it did not affect that of the ones having the hydroxyl group. The presence of C-2 double bond, as in GA5 and deoxy-GA5, diminished the inhibitory action of DGC. The DGC inhibition was alleviated by raising the doses of the relevant GAs, suggesting that it is a competitive inhibition. These results and the finding that the growth of normal maize and rice seedlings are inhibited by DGC indicate that GA9, GA19, GA20 or other gibberellins having ring A of the same structure are involved in the growth of these plants as active form(s) or as intermediate(s) leading to the active form(s).

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